U.S. Pat. No. 5,692,472 discloses that a maximum permissible engine torque or a maximum permissible engine power is derived on the basis of at least one operating variable, for example, the accelerator pedal position. This maximum permissible engine torque or maximum permissible engine power is compared to the actual torque or the actual power of the drive unit. Fault reaction measures are initiated when the actual value exceeds the maximum permissible value. These measures can include switching off the metering of fuel until the actual value again drops below the maximum permissible value.
With the monitoring measures described, there is a conflict of objectives with respect to the functionality of the drive unit and the precision of the described monitoring. At least in some operating states such as when the accelerator pedal is in the idle position, a relatively large torque or a relatively large power must be permitted so that the idle control can compensate for disturbance quantities such as a switched-in climate control compressor, a steering-assist pump or a grinding of the clutch. In such operating situations, the maximum permissible values must be set to values which can already lead to an unwanted acceleration of the vehicle in the case of a fault.